Step-by-step operating mechanism



Feb. 8, 1944. JQINES 2,341,182

STEP-BY-STEP OPERATING MECHANISM Filed Oct. 17. 1941 Patented Feb. 8, 1944 STEP-BY-STEP OPERATING MECHANISM Jesse E. Jones, Wauwatosa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application October 17, 1941, Serial No. 415,379

7 Claims.

This invention relates to a step by step operating mechanism and is especially adapted to the operation of rheostats and the like.

In practice it is frequently required to operate a variable resistance rheostat at a slow rate from a high or maximum resistance position to a low or minimum resistance position, or vice versa. If the rheostat carries a substantial current, it is desirable to move the contacts from point to point throughout the range of operation in a step by step motion, so that the resistance between a movable contact and the stationary contact is during most of the time a minimum, i. e., the respective contacts register with each other. Otherwise the contacts are subject to excessive heating, pitting and wear due to arcing therebetween.

The aforementioned condition is also of importance if the device is an inductance, operating on alternating current. In the latter case the bridging of two or more adjacent stationary contacts by the movable contact brush must be limited in time, in order to avoid overheating of that section of the inductance, which carries the short-circuit current due to such bridging of contacts.

An object of the present invention is to provide an improved step by step drive of the aforementioned character.

Another object is to provide a reversible step by step drive of extremely simple construction.

Another object is to provide a reversible step by step drive actuated by a reversible motor.

Another object is to provide a drive of the aforementioned type in which the direction of movement of the driven member is reversed upon reversal of the driving motor.

Another object is to provide a multiple contact rotary switch in which the movable contact is moved in a step by step motion into and out of engagement with the successive contacts so as to register squarely therewith sequentially.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates a preferred embodiment of the invention.

The system illustrated comprises a resistor I, having a plurality of taps each connected to one of a plurality of contacts 2. The rheostat may be connected into a circuit to be controlled in any well known manner. A pivoted gear wheel 3 is provided at its circumference with gear teeth. 5. Contact brushes and 6, respectively, are attached to but insulated from the wheel 3 to rotate therewith, and are conductively connected v With each other. The brush 5 is arranged to enease the contacts 2, while the brush 6 makes contact with a stationaryv contact ring 1, arranged concentric with the wheel 3. The wheel 3 is further provided with an abutment 8 which, upon the brush 5 having-been moved into engagement with one or the other of the end contacts 2, according to the direction of rotation of wheel 3, acts to open normally closed stationary limit switches 9 or ID, selectively.

The apparatus further includes a reversible motor H, having built-in change-speed gearing, as indicated at l3. Motor l I has reversing terminals II and li and a common terminal H The motor may be of any desired reversible type and the method of its control forms no part of the present invention. The terminal H is connected to the line L of a current supply L L The line L is connected to the center terminal I2 of a reversing switch l2, which is provided with stationary contacts l2 and I2 selectively engageable by a contact lever I2 The contact I2 is connected through the limit switch 9 to the motor terminal II, and the contact l2 is connected through limit switch I0 to motor terminal ll The shaft 14 of motor II is mounted in suitable bearings, and is provided with a crank lever IS, the outer end of which carries a roller Hi. When the power required to be transmitted by the lever I5 is small; as where rack memberand gear wheel of relatively small size are employed, a pin fixed to lever I 5 may be substituted for the roller [6. A rack l! is guided near one end thereof for sliding and oscillatory motion in a suitable bearing l8. Intermediate its length the rack 11 is provided with a gear tooth is which is adapted to mesh with the teeth 4 of the wheel 3. A plurality of teeth like [9 may be employed if desired. At its other end the rack I1 is provided with an inverted U-shaped extension Il of substantially rectangular contour, the inner surfaces 2t, 2| and 22 of the three walls of which are adapted to be engaged by the roller l6 and to act as cam surfaces or a track in conjunction with the latter. The surfaces 28 and 2| are so arranged that, in the lower position of rack 17 illustrated, they are substantially parallel to a line connecting the center of wheel 3. with the point of engagement of the tooth [9. The surfaces 20 and 2| are joined by the transverse surface 22 to form an inverted U. In the embodiment illustrated the distance between the parallel surfaces 20 and 2| is equal to the diameter of the circle described by the circumference of the roller I6 upon rotation of the arm l5, less the desired tangential movement of the teeth 4 for one step of motion, which is usually equal to the circumferential pitch of teeth 4. The surface 22 is so arranged that as an incident to engagement thereof by roller IS the extension l1" of lever I! is lifted sufliciently to effect disengagement of the tooth l9 from the teeth 4.

It will be apparent that when the crank lever is rotated counterclockwise, the rack I1 is reciprocated back and forth by the distance of a tooth pitch. During the movement of the rack I! to the right the tooth I9 is engaged with the wheel 3, and as the lever l5 moves from the position thereof illustrated in a counterclockwise direction the roller engages surface to effect movement of rack i1 toward the right, until the extreme right-hand position of the latter is reached. Thereupon clockwise rotation of the wheel 3 ceases, while the brush 5 rests squarely on one of the contacts 2. The angular pitch of said contacts is equal to the angular pitch of the teeth 4. Shortly after the movement of rack l! to the right ceases, the roller it engages the surface 22 and lifts the rack ll, thereby effecting disengagement of the tooth l9 from the teeth l. After the lever is has passed through its upper vertical position the roller it remains for a time in engagement with surface 22, permitting a slight degree of lowering of rack ll. When the roller It comes into engagement with surface 2!, the tooth l9 still clears the teeth 4. Further rotation of the lever l5, by engagement of roller IS with said surface 2| effects movement of the rack I? to its extreme left-hand position, at the same time permitting a further degree of lowering of tooth is without engaging the same with teeth 4. Thereafter further rotation of lever 15 permits the tooth l9 to drop abruptly or substantially Vertically into the next space between two teeth 4. The operation described is repeated at every revolution of the lever I5.

It will readily be seen that with the parts in the respective full line positions illustrated upon reversal of rotation of the motor H, the tooth is is first lifted out of engagement with teeth l, then carried to the right and dropped into engagement with teeth 4 one space to the right of the full line position of tooth is illustrated; whereupon the rack is moved toward the left to effect counterclockwise movement of wheel 3 to a degree corresponding to the clockwise movement aforementioned. Hence reversal of motor I I by operation of switch 12 causes corresponding reversal of the step by step movement of rheostat wheel 3.

When the abutment 8 makes contact with either of the limit switches ID or 9, the cycle of operation of the motor in the corresponding direction is interrupted.

The proportions of the cam surfaces 20, 21 and 22 and the lever [5 may be such, that for each revolution of lever iii the degree of rotation of the wheel 3 is a multiple of the circumferential pitch of teeth 4. It will also be apparent that the cam surfaces 20, 2| and 22 need not be straight line surfaces as shown, but that they may be suitably curved. It is only necessary that they be correlated to the lever l5 and roller [6 in such a manner that the tooth I9 is in engagement with the Wheel 3 for a desired distance and that the rack IT. can move in the reverse direction without interference with the wheel 3.

The specific embodiment of my invention herein disclosed is intended primarily to provide an extremely slow motion rheostat drive; as, for instance, one in which approximately one-half hour is required for full travel of the contactor from one end to the other of the rheostat. Such a rheostat is adapted for use in conjunction with a paper coating machine and will cycle continuously to control the moisture content or humidity of the paper.

In this connection it is to be noted that the construction illustrated lends itself admirably for permitting disconnection of the ratchet lever ll from the rheostat gear 3 (as by merely manually lifting the former); whereas the rheostat may then be readily reset as by manually moving the abutment 8 or a special manually operable handle (not shown).

The device disclosed is therefore generally useful in systems requiring slow motion of the rheostat bu-t enabling quick resetting of the latter manually or otherwise. Thus the device is of great utility when employed in conjunction with. a machine for winding paper, cloth, metal strip, or any other material of web form; wherein the slow motion rheostat will operate to change the field strength of the motor driving the winder, to maintain the proper tension and speed characteristics of the paper strip as the roll diameter builds up. In such an installation the rheostat will preferably be manually reset prior to starting the winding of each new roll.

The step by step operating mechanism herein disclosed is, of course, not limited to use in controlling a single rheostatic circuit. Thus a single mechanism of the character aforedescribed may be utilized to drive two or more rheostats operat ing in separate circuits. For instance, where two motors are employed to pass a web of cloth back and forth through a dye vat, the motors are respectively adapted to drive rolls onto one of which the web is wound and from the other of which said web is simultaneously unwound. In such an installation, the herein described slow motion mechanism would preferably be arranged to drive the movable elements of two rheostats (arranged on opposite sides of a single gear, such as 3), and

said rheostats would be so connected relatively to their associated circuits that the field of one of the motors would be strengthened simultaneously with the weakening of. the field of the other motor; so as to maintain the motor torques in proper relationship to the relative thicknesses of the wound material upon the respective rolls, thus enabling maintenance of a substantially constant tension upon the web of material between the rolls during the entire winding and or unwinding operation. As aforeindicated, the rate of movement of the contactors of the rheostats would be synchronized with the rate of change of diameter of the respective rolls of web material.

I claim:

1. A step by step operating mechanism comprising, in combination, a movable member having gear teeth formed thereon, a rack comprising a single rigid element and supported near one end thereof for combined reciprocatory and transverse movement in the plane of said member and having at least one tooth adapted for cooperation with said gear teeth, a crank, means for continuously rotating said crank, and said rack being provided near its other end with a plurality of track surfaces formed thereon and arranged in the form of an inverted U, said sur-- faces being sequentially engaged by said crank during each complete rotation of the latter, whereby said combined reciprocatory and transverse movement of said rack is utilized to effect step by step movement of said movable member in a given direction in synchronism with the rotation of said crank.

2. A step by step operating mechanism comprising, in combination, a movable member having gear teeth formed thereon, a rack comprising a single rigid element and supported near one end therefor for combined reciprocatory and transverse movement in the plane of said member and having at least one tooth adapted for cooperation with said gear teeth, a crank, means for continuously rotating said crank, said rack being provided near its other end with a plurality of track surfaces formed thereon and arranged in the form of an inverted U, said surfaces being sequentially engaged by said crank during each complete rotation of the latter, whereby said combined reciprocatory and transverse movement of said rack is utilized to effect step by step movement of said movable member in a given direction in synchronism with the rotation of said crank, and said rack tooth bein manually disengageable from said gear teeth at will, to thereby permit movement of said movable member to any desired position subject to manual control, for the purpose set forth.

3. A step by step motion mechanism comprising, in combination, a crank, a rotatable wheel, and a rack comprising a single rigid element and supported near one end thereof for combined reciprocatory and transverse movement in the plane of said wheel and adapted to engage said wheel, said rack being provided near its other end with a track arranged in the form of an inverted U and adapted to be engaged by said crank for causing said rack to intermittently engage said wheel and rotate it step by step in a given direction in synchronism with the rotations of said crank.

4. A step by step motion mechanism comprising, in combination, a crank, a rotatable gear, a rack arranged for combined reciprocatory and transverse movement in the plane of said gear, said rack having a detent adapted to engage said gear, and said rack being further provided with a track arranged in the form of an inverted U and adapted to be engaged by said crank during each rotation of the latter for causing said rack to engage said gear and rotate it through a predetermined angle in a given direction in synchronism with the rotation of said crank.

5. A reversible step by step motion mechanism comprising, in combination, a crank, a gear, a rack comprising a single rigid element, and a fixed support for one end of said rack affording combined reciprocatory and transverse movement of said rack in the plane of said gear, said rack having a detent adapted to engage said gear, and being provided near its other end with a track arranged in the form of an inverted U and adapted to be engaged by said crank for causing said rack to intermittently engage said gear, and move it step by step in a given direction in synchronism with the rotations of said crank, and to reverse the direction of movement of said gear upon reversal of the direction of rotation of said crank.

6. A regulator for controlling an electric circuit comprising, an impedancehaving a plurality of stationary contacts arranged in side by side relation for varying the amount of said impedance included in an electric circuit, a contactor adapted to complete a circuit with only one of said contacts selectively, a gear operatively connected with said contactor to move the same in a step by step motion from one of said contacts to another selectively, a reversible motor, means for energizing said motor to rotate it in opposite directions selectively, a crank rotated by said motor, a rack comprising a single rigid element and adapted to engage a support at one end thereof, a support for said rack affording combined reciprocatory and transverse movement of said rack in the plane of said gear, said rack having a detent adapted to engage said gear, said rack also being provided with a track arranged in the form of an inverted U and adapted to be engaged by said crank for causing said rack to intermittently engage said gear to rotate said gear step by step in a given direction upon the rotation of said motor, so as to cause said contactor to register with one of the contacts at the end of each step and to reverse the direction of rotation of said gear upon reversal of the direction of rotation of said motor, means to effect deenergization .of said motor when said gear reaches its limit of travel in the respective direction, and said rack being manually disengageable under all conditions to render said detent ineffective, whereby said contactor may be reset to any desired position, for the purpose set forth.

7. In an operating mechanism for a circuit commutating device or the like, said device being provided with stationary contacts arranged in side by side relation, and with a contactor adapted to complete a circuit with any one of said contacts selectively, the combination of a gear operatively connected with said contactor to move the same in a step by step motion from one of the contacts of said device to another, a reversible motor, means for energizing said motor to rotate it in opposite directions selectively, a crank rotated by said motor, a rack comprising a single rigid element and adapted to engage a support at one end thereof, a support for said rack aifording combined reciprocatory and transverse movement of said rack in the plane of said gear, said rack having a detent adapted to engage said gear, said rack being also provided with a track arranged in the form of an inverted U and adapted to be engaged by said crank for causing said rack to intermittently engage said gear to rotate said gear step by step in a given direction upon the rotation of said motor, so as to move said contactor to register with one of the contacts at the end of each step and to reverse the direction of rotation of said crank upon reversal of the direction of rotation of said motor, and said rack being manually disengageable under all conditions to render said detent ineiTective whereby said contactor may be reset to any desired position for the purpose set forth.

JESSE E. JONES.

- CERTIFICATE or CORRECTION. Patent No. 2,5u1,182. February 8, 1 m.

. JESSE E. JONES.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 9, claim 2, strike out "therefor" and insert instead -'thereof--;

same column, line 15, claim )4, strike out "arranged" and insert instead "comprising a single rigid element and upported nearone end thereof-;

line 11.6, sane claim, after "provided" insert -nes.r its other end-; and

that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office Signed and sealed this 9th day of May, A. D. 191414..

Leslie Frazer (Seal) Acting Commissioner of Patents.

, column, line 9, claim 2, strike out "therefor" and insert instead '-thereof--- CERTIFICATE OF CORRECTION. Patent No. 2,5l4l,l82. February 8, 19M.

- JESSE E. JONES.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows; Page 5, first 5 same column, line 14.5, claim 1;, strike out "arranged" and insert instead "comprising a single rigid element and supported near-one end thereof--; line 1+6, same claim, after "provided" insert -near its other end; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 9m day of May, A. D. 19%.

Leslie Frazer (Seal) Acting Commissioner of Patents. 

